The results of the present study showed that the administration of an IV bolus of 500 mL of normal saline in the ambulatory setting is safe and results in significantly larger LAA dimensions. Sizing based on post volume loading measurements taken pre-procedurally significantly improved the agreement between the predicted device size determined by the manufacturers’ recommendations and the final size of the device implanted.
LAA closure has emerged as a mechanical alternative to pharmacological stroke prevention in patients who cannot tolerate oral anticoagulation [
4,
5,
12]. However, in order to optimize procedural success and reduce periprocedural complications that may offset the efficacy of the procedure, appropriate sizing of the occluder device is of paramount importance. Undersizing may result in device migration or inadequate sealing of the LAA cavity, which in turn could lead to peridevice leaks, thrombus formation and embolic stroke. On the other hand, excessive oversizing may lead to physical expulsion of the device from the LAA and may cause pericardial effusion/ tamponade due to perforation [
13,
14]. Baseline preprocedural TEE to screen candidates for LAA closure is performed under fasting conditions, which may reduce intravascular volume and lead to inadvertent undersizing of the LAA. We observed an average increase of approximately 1.5 mm in the LZ and depth after volume loading, confirming the notion that the LAA is a compliant structure dependent on volume status. Previous studies have shown a similar, albeit slightly higher, increase of ∼2 mm in the width and depth of the LAA after volume loading [
7,
8], which is clinically relevant since it likely results in upsizing the occluder device by an entire size. The likely reason for the more modest increase in size found in the herein cohort is the fact that the aforementioned studies administered on average a higher fluid bolus (∼800–1000 ml), and relied on invasive left atrial pressure monitoring to ensure adequate volume status. In the ambulatory setting, since invasive hemodynamic monitoring is not feasible and IV fluid administration may trigger some complications such as pulmonary edema, particularly in patients with reduced LVEF, we opted to give a smaller volume of normal saline. This strategy proved to be well tolerated, and all examinations were performed without any adverse events. Moreover, the predicted device size based on the LZ dimensions taken post volume loading correlated well with the device size that was actually implanted in 71% of patients. Conversely, similarly to what has been previously reported [
8], sizing based on the 2D maximum diameter of the LZ before volume loading correlated poorly with the device size finally selected (42%). It is noteworthy that the timing and optimal volume of the saline infusion should be the object of further studies. An individualized dose of saline taking into account LVEF and adapted to body surface area might be a better choice. Also, volume loading might be administered before TEE probe insertion, however, it is important to take into account that the physiological effects of a fluid bolus typically dissipates within the hour [
15].
During the evaluation phase of patient suitability for LAA closure, being able to accurately define the anatomy and predict the device to be implanted is crucial as it allows for the Heart Team to make a more informed preprocedural evaluation. For instance, one of the most commonly used devices, the Watchman device, requires an implant depth equal to the orifice diameter, and thus cannot be implanted in a shallow LAA. As such, one benefit of administering a volume loading during preprocedural evaluation is to avoid contraindicating the procedure on the basis of on an incorrect depth. This is also applicable to other devices, where an incorrect measurement can erroneously contraindicate a procedure. It is of note that the use of 2D imaging to define the varied and complex morphology of the LAA may fail to depict its true dimensions, and other imaging techniques/modalities such as real time 3D-TEE and multidetector computed tomography-based LAA sizing may be more accurate methods, especially if undertaken in an euvolemic state [
8,
16,
17]. Also, some authors have suggested performing the LAAC procedure with no procedural TEE guidance in order to avoid general anesthesia and facilitate patients’ recovery [
9‐
11]. In these cases, procedural LAAC guidance is based on fluoroscopy [
9] or intracardiac echocardiography [
10,
11], and device sizing is mainly based on pre-procedural TEE measurements. In such cases, the strategy of volume loading during pre-procedural TEE would be key in order to provide reliable measurements and avoid complications related to inaccurate device sizing.
Limitations
Our study has several limitations. This report consisted of an observational single-center study with a retrospective analysis and a relatively small number of patients, which limits the strengths of our results. Imaging the LAA may be challenging in some cases and it was not always possible to obtain identical images before and after volume loading. Also, observer variability was not investigated, and the lack of blinding regarding patients’ fluid status may have introduced some degree of measurement bias. However, in order to reduce interobserver variability and maintain consistency, all studies were analyzed by a single measurer and the magnitude of increase in LAA size found in our cohort was consistent with previous studies [
7,
8]. Additionally, due to logistical and technical reasons, we were unable to analyze 3D data, which is in theory a more accurate method to size the LAA and might have yielded larger dimensions. Some patients might have started with an adequate volume status, which might be one of the reasons for the smaller increase in LAA dimensions found in some cases. Lastly, regarding the safety of administering a 500 ml IV fluid bolus, even though the procedure was well tolerated by all patients included in the cohort, we acknowledge that the size and design of the study does not lend itself to generalize our results since patients with heart failure and reduced LVEF were in the minority.